WASHINGTON, D.C. ( TheStreet) -- U.S. regulators posed some tough questions about the efficacy and safety of Human Genome Sciences' ( HGSI) experimental lupus drug Benlysta in a review posted ahead of next Tuesday's advisory panel meeting.

Investors largely expect Human Genome Sciences and partner GlaxoSmithKline ( GSK) to receive approval for Benlysta, which would be the first new treatment for the autoimmune disease lupus in about 50 years. To achieve the goal, however, Benlysta must first pass muster from a panel of outside experts and then receive final approval from the U.S. Food and Drug Administration.

Friday's medical review of Benlysta, posted on the FDA's web site, is the first step in this process. The FDA tends to take a prosecutorial role in its drug reviews ahead of advisory panel meeting, so investors largely anticipated the questions and concerns raised about Benlysta.

Across two large clinical trials, FDA acknowledged that two large clinical trials demonstrated a statistically significant difference in the number of lupus patients who responded to treatment with Benlysta compared to placebo. However, FDA said the results from the Benlysta studies produced "somewhat marginal efficacy" in part because the drug's biggest positive effect was on organ systems in patients that are not life threatening. The FDA also found that the study conducted outside the U.S. also produced stronger results than the study conducted here and African-Americans lupus patients underperformed relative to non-African Americans.

The FDA also raised some concerns about Benlysta's safety, including risk for infections and neuropsychiatric adverse events including suicide. The specter of an increased risk of suicide was probably the most surprising revelation in the FDA material.

"Clearly there is a need for effective therapies in SLE lupus ," FDA concludes. "However whether belimumab's Benlysta's benefits sufficiently outweigh its risks is the crux of the issue... If belimumab only has a modest effect for some patients and manifestations, is a possible increased risk of death, infection, or neuropsychiatric adverse effects worth the potential benefit?"

That's the question which will be answered Tuesday when the FDA's panel of outside experts convene and decide whether to recommend Benlysta for approval, or not.

If you liked this article you might like

Stock Futures Waver as Earnings Season Begins

Stocks to Watch: WellPoint, Amerigroup, Alcoa (Update 1)

5 Things You Should Know Before the Stock Market Opens

Celgene Not Buying Human Genome Sciences

Human Genome Sciences Inc (HGSI): Today's Featured Health Care Winner